/*---------------------------------------------------------------------------*\
  =========                 |
  \\      /  F ield         | foam-extend: Open Source CFD
   \\    /   O peration     | Version:     4.1
    \\  /    A nd           | Web:         http://www.foam-extend.org
     \\/     M anipulation  | For copyright notice see file Copyright
-------------------------------------------------------------------------------
License
	This file is part of foam-extend.

	foam-extend is free software: you can redistribute it and/or modify it
	under the terms of the GNU General Public License as published by the
	Free Software Foundation, either version 3 of the License, or (at your
	option) any later version.

	foam-extend is distributed in the hope that it will be useful, but
	WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
	General Public License for more details.

	You should have received a copy of the GNU General Public License
	along with foam-extend.  If not, see <http://www.gnu.org/licenses/>.

Description
	The function renumbers the addressing such that the band of the
	matrix is reduced. The algorithm uses a simple search through the
	neighbour list


\*---------------------------------------------------------------------------*/

#include "bandCompression.H"
#include "SLList.H"

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

// Constructor from components
Foam::labelList Foam::bandCompression(const labelListList& cellCellAddressing)
{
	labelList newOrder(cellCellAddressing.size());

	// the business bit of the renumbering
	SLList<label> nextCell;

	labelList visited(cellCellAddressing.size());

	label currentCell;
	label cellInOrder = 0;

	// reset the visited cells list
	forAll (visited, cellI)
	{
		visited[cellI] = 0;
	}

	// loop over the cells
	forAll (visited, cellI)
	{
		// find the first cell that has not been visited yet
		if (visited[cellI] == 0)
		{
			currentCell = cellI;

			// use this cell as a start
			nextCell.append(currentCell);

			// loop through the nextCell list. Add the first cell into the
			// cell order if it has not already been visited and ask for its
			// neighbours. If the neighbour in question has not been visited,
			// add it to the end of the nextCell list

			while (nextCell.size())
			{
				currentCell = nextCell.removeHead();

				if (visited[currentCell] == 0)
				{
					visited[currentCell] = 1;

					// add into cellOrder
					newOrder[cellInOrder] = currentCell;
					cellInOrder++;

					// find if the neighbours have been visited
					const labelList& neighbours =
					    cellCellAddressing[currentCell];

					forAll (neighbours, nI)
					{
					    if (visited[neighbours[nI]] == 0)
					    {
					        // not visited, add to the list
					        nextCell.append(neighbours[nI]);
					    }
					}
				}
			}
		}
	}

	return newOrder;
}


// ************************************************************************* //
